An image reproducing system has functions of storing image data obtained from scanning of an original picture into a memory and recording a photosensitive film by using the image data being read from the memory.
Conventionally, several ways of converting magnification ratio in reproducing images are known, one of which is for example the method disclosed in U.S. Ser. No. 924,928, now abandoned. This method is characteristic of varying revolution frequency and feeding speed of an input head in the sub-scanning direction according to a specified magnification ratio while fixing revolution frequency and feeding speed of a recording head in the sub-scanning direction to reproduce an image with magnification conversion. And in this method, both frequencies of a writing pulse for inputting an image data to a memory and a reading pulse for outputting the image data from the memory are identical or in a certain ratio.
Secondly, the method disclosed in U.S. Pat. No. 3,272,918 can be exemplified. The method is described as follows. For the sub-scanning direction factor, magnification conversion is attained by varying feeding speed of a recording head while fixing feeding speed of an input head. For the main scanning direction factor, magnification conversion is attained by varying frequency ratio of a writing pulse and a reading pulse for an image data when being input to or output from a memory while fixing revolving speed of both drums. In this, as the reading pulse has a constant frequency, the magnification conversion is attained by varying frequency of the writing pulse, which has a higher frequency when a reproduced image is to be expanded and has a lower frequency when a reproduced image is to be contracted.
Other from the abovementioned two methods, the method disclosed in U.S. Pat. No. 4,163,605 or in U.S. Ser. Nos. 933,714 now abandoned or 170,127 now abandoned can be cited. The method adopts the following way to vary magnification ratio. While fixing revolution frequency of an original picture drum and a recording drum, and feeding speed of the recording head in the sub-scanning direction, magnification conversion for the sub-scanning direction factor is attained by varying feeding speed of the input head, and magnification conversion for the main-scanning direction is attained by fixing a relation between a writing pulse frequency and a reading pulse frequency at 1:1, and by reading an image data from said memory in a skipped or in an overlapped fashion of their addresses.
The abovementioned three methods function well for magnification conversion of the main scanning direction factor, but magnification conversion for the sub-scanning direction factor is attained only by varying relative feeding speed of between the input head and the output head.
However as it is difficult to vary the diameter of an input scanning beam smoothly, an uneven density distribution of a reproduced image is unavoidable in the prior art even when magnification ratio is varied by using any one of aforesaid methods.